U.S. patent number 4,753,499 [Application Number 06/392,695] was granted by the patent office on 1988-06-28 for joining of optical fibre cables.
This patent grant is currently assigned to British Telecommunications. Invention is credited to Peter J. Clarke, Prem G. Malkani.
United States Patent |
4,753,499 |
Malkani , et al. |
June 28, 1988 |
Joining of optical fibre cables
Abstract
Optical fibre based cables 1 and 2 are jointed by fixing their
axial strength members 3 to a perforated connecting member 9. Fibre
tails to be joined are stored on the connecting member by winding
around guides 16 engageable with perforations 11. Fibre end parts
are joined and positioned in ferrules 24 also engaged with
perforations 11.
Inventors: |
Malkani; Prem G. (Pinner,
GB2), Clarke; Peter J. (Thatcham, GB2) |
Assignee: |
British Telecommunications
(London, GB2)
|
Family
ID: |
10525026 |
Appl.
No.: |
06/392,695 |
Filed: |
June 28, 1982 |
Foreign Application Priority Data
Current U.S.
Class: |
385/135 |
Current CPC
Class: |
G02B
6/444 (20130101) |
Current International
Class: |
G02B
6/44 (20060101); G02B 006/36 (); G02B 007/26 () |
Field of
Search: |
;350/96.20,96.23,96.16,96.21 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Cos 2 Experiment in Turin: Field Test on an Optical Cable in Ducts;
Cocito et al.; IEEE Transactions on Communications; vol. Com-26,
No. 7; Jul. 1978; pp. 1028-1035. .
IEEE Transactions on Communications, vol. Com-26, No. 7, Jul. 1978,
pp. 1028-1035, IEEE, New York, USA G. Cocito et al., Cocito et al.,
"Cos 2 Experiment Cable in Ducts" p. 1031 left-hand column, line
13, p. 1032, left-hand column, line 7, FIG. 9..
|
Primary Examiner: Sikes; William L.
Assistant Examiner: Wise; Robert E.
Attorney, Agent or Firm: Kemon; Solon B.
Claims
We claim:
1. A joint between two optical fibre based cables each comprising
an optical fibre, usually sheathed, within an outer cover, the
fibres projecting for splicing as elongated tails, such joint also
comprising a connecting member having a plurality of perforations,
clamps on the connecting member gripping the cables by the outer
covers with the tails extending over the connecting member and
being spliced together and a plurality of guides each having a stem
for detachable engagement with a perforation on the connecting
member detachably connected each to a location on the connecting
member, the elongate tails being wound after splicing around the
guides for storage on the connecting member, appropriately
positioned to accommodate the length of the fibre after splicing
wth the minimum bend radius of the fibre not being exceeded.
2. A joint according to claim 1 wherein strength members of the
cables are secured to the connecting member.
3. A joint according to claim 2 wherein the connecting member
comprises an elongated flat rigid member having securing means for
the strength members adjacent either end.
4. A joint as claimed in claim 3 wherein the said member is
disposed diametrically within a generally cylindrical casing having
a transparent wall part.
5. A joint according to claim 1 including carriers for joined fibre
end parts said carriers also being detachably securable to a
selected one of a plurality of locations.
6. A joint as claimed in claim 5 wherein each carrier comprises a
channel to receive joined fibre end parts extending between stems
for detachable engagement with a perforated support structure.
7. A joint as claimed in claim 1 wherein each guide comprises an
openable frame through which a fibre passes.
8. A joint as defined by claim 7 wherein said frame is rendered
openable by means of a hinge resiliently biased to the closed
position.
9. A method of forming a joint between optical fibre based cables
each comprising a cover and at least one optical fibre such method
comprising the steps of:
detaching elongated fibre tails from the cables to be joined;
clamping the cables by the outer covers to a perforated connecting
member with the fibre tails extending,
splicing the fibre tails at a location remote from said connecting
member,
applying to the perforated surface of said connecting member a
selected number of guides each having a stem in detachable
engagement with a perforation of the surface, the number and
location of the guides being chosen so as to provide a guide track
for the excess length of joined fibre,
and winding the said excess length around the guide in a stored
configuration without exceeding the minimum end radius of the
fibre.
Description
DESCRIPTION
This invention relates to the joining of cables based on optical
fibres.
It is an objective of the present invention to provide a joining
assembly for a cable based on optical fibres which enables exposed
fibres to be joined at a location spaced from the juxtaposed cables
and the resultant relatively long lengths of fibre to be stored
after joining on the assembly without the bending of fibres beyond
their minimum bend radius.
In accordance with the present invention there is provided a
joining assembly for at least two cables each comprising an optical
fibre and a strength member, such assembly comprising a connecting
member, means for securing the strength members of the cables to
the connecting member and guides for the fibres at least some of
which are detachably securable to a selected one of a plurality of
discrete locations, preferably on the connecting member.
In use the cables are initially secured together by fixing the
strength members of each cable to the connecting member with the
desired length of fibre exposed as an elongate fibre tail. The
fibre tails are spliced together by a suitable device and the
excess length of fibre constituted by the joined and spliced tails
is accommodated by winding around the guide members which can be
appropriately positioned to suit the length of fibre at selected
locations on the connecting member. The guide members will be so
disposed that the fibre is not bent beyond the minimum bend
radius.
In an embodiment a rigid, for example metal, connecting member has
a flat region uniformly perforated to provide the discrete
locations. The guide members have stems for insertion into and
engagement with the perforations and parts around or through which
the fibre tails are led. The exposed fibre ends are fixed together
and secured in a carrier also having one or more stems for
selective positioning on the perforated flat region. This
positioning is also chosen to avoid detrimental bending of the
fibre.
The cable with which the invention is primarily concerned is
intended for inland use and comprises a central axially extending
strength member, usually of wire strands, a plurality of optical
fibres each sheathed in plastics surrounding the strength member
and an outer protective casing. Other elements or layers for
example electric conductors can be included.
With the embodiment set out above the central strength member is
fixed to the rigid connecting member and the electrical conductors
pass under the flat region for interconnection.
The invention further provides a completed joint with two of the
cables joined by the assembly set out above, the assembly and
joined cables being surrounded by a protective outer casing. The
connecting member can extend diametrically across the interior of a
cylindrical casing, conveniently with a transparent wall portion so
that the orientation and condition of the joint can be visually
monitored.
A particular embodiment of the invention will now be described by
way of example and with reference to the accompanying drawings
wherein:
FIG. 1 is a sectional view through an optical fibre connection in a
cased jointing assembly;
FIG. 2 is a detail on a larger scale showing the joining of fibre
ends;
FIG. 3 is an end view of the detail of FIG. 2, and
FIGS. 4 and 5 are further details showing guide members engaged
with a perforated support.
Referring initially to FIG. 1 of the drawings cables 1 and 2 to be
joined each comprise a central strength member 3 constituted by
wire strands, termed a king wire and a plurality of optical fibres
4 (one fibre only is illustrated for each cable) surrounding the
king wire 3 and an electrical conducting wire 5 (with an insulating
cover). Each cable further comprises an outer plastics cover 6.
Each optical fibre is contained within a fitting plastics
sheath.
A connecting assembly for joining together the cables 1 and 2
comprises an elongated shallowchannel shaped metal member 8 with a
flat web 9 and shallow side flanges or rims 10. The member 8 is
formed of sheet material perforated over the entire area (except
for the end parts) with round holes 11 (some only shown in FIG. 1).
Each hole has a diameter of approximately 0.5 centimeter, the
periphery of each hole 11 being separated from the peripheries of
adjacent holes by approximately 0.3 centimeter. At each end of the
connecting member 8 there is positioned a clamp 12 for the cable
outer cover. Each clamp 12 comprises an upper and lower member held
together by screws 13 passing through web 9 to be engaged by nuts
and having U-shaped recesses so as to define together a cylindrical
clamping bore dimensioned to recieve the cover. Longitudinally
inwardly with respect to each clamp 12 is a bolt 14 having an
apertured stem through which the king wire 3 is inserted. A nut on
the underside of the plate engages the bolt 14 thereby firmly to
clamp the king wire against the upper surface of web 9. This fixing
of each king wire transmits the principal axial stresses from the
cable to and through the connecting member 8. Between the bolt and
the cable clamp is a rubber or plastics lined bore 15 through which
emerging conductor wire 5 can pass and traverse along the underside
of the web 9.
A plurality of optical fibre guides 16 are detachably engaged with
the web 9. These guides 16 will be described with reference to
FIGS. 4 and 5 of the accompanying drawings. Each guide 16 is formed
of a relatively stiff and strong self-supporting plastics material
such as a polyamide resin and has a frame member 17 through which
the fibre is passed and a dependant stem 18. The frame member is of
generally rectangular configuration with the upper wall defined by
first and second members 19 hingedly connected to the upstanding
frame side members, the end parts of members 19 having
interengaging hooks 20. The dot and pick lines show the hinged
members 19 in the open position at which an optical fibre can
readily be inserted into the frame. On depressing the hinged member
19 to the position shown in solid line the frame is closed by
interengagement of the hooks 20. The stem 18 has barbs 21 and above
the barbs outwardly extending arms 22. The barbs are inserted
through the selected perforation 11 expanding laterally outwardly
to prevent withdrawal of the stem 18, location against upward
movement being provided by the arms 22.
Referring now to FIGS. 2 and 3 ferrules 23 for carrying spliced
fibre tails are provided. Each ferrule 23 has a short trough 24 of
channel section extending between supports 25 having lower parts
similar to those of guides 16 and identified on the drawings with
corresponding reference numerals. These supports 25 are so spaced
that the ferrules 23 can be selectively positioned on web 9.
The protective housing for the completed joint comprises two end
caps 26 with axial sockets 27 to receive entering cables 1 and 2. A
rigid cylindrical and transparent tube 28 extends between inwardly
extending rims 29 of caps 26. The web 9 extends diametrically
across tube 28 and is located by its tight fit with, if desired,
protrusions from the web fitting into slots in rims 29. A sealing
sleeve 30 at each end bridges tube 29 and cap 26. Two bands 31, 32
of shrinkdown sleeving are provided at each end to connect the tube
28 to the cap 26 and the cap 26 to the incoming cable respectively.
If the joint is to be pressurised then an air valve may be fitted
in one of the caps 26, thus allowing the valve to be better
protected than if it were fitted in tube 29. Additionally the valve
may be fitted into a cap 26 during manufacture rather than in the
field, thereby allowing a higher quality standard to be
maintained.
To remove the tube 28 for joint maintenance the band 31 of heat
shrinkable material between collar cap and the sleeve 30 is heated
and slit with a sharp knife. The band may then be removed and the
sleeve 30 slid to one side. As any air valve is located in a collar
26 the risk of damage to the valve is reduced during maintenance.
After maintenance the joint may be readily resealed by sliding the
sleeve 30 back over the collar 26 and a longitudinally slit sleeve
of heat shrinkable material used to replace the original band
31.
The connecting assembly will be further described by reference to a
typical splicing operation.
By way of introduction it should be explained that the end to end
splicing of optical fibres is a difficult operation and may require
several attempts. The splicing is carried out on a machine which
has to be located at a position reasonably remote from the cable
end. Thus a substantial length of fibre needs to be unsheathed from
the cable prior to the splicing operation.
Thus a fibre tail, that is a fibre with its individual sheath, is
exposed by cutting away the outer cover 6. The king wires 3 are
then fixed as described above and the outer covers of the cables
secured by clamps 12. The two fibre tails to be joined are taken to
the splicing machine. The individual sheaths are stripped off the
tail end parts and the fibre ends spliced together and placed in
the channel shaped trough 24 of a ferrule 25 and fixed there with a
mass 33 of settable resin (see FIGS. 2 and 3). A suitable number of
the guide members 16 are then positioned as a trackway around the
periphery of perforated web 9 and spare fibre ends wound around it.
Entry guide 16e leads one of the fibres 4 into the peripheral track
way and a guide 16f leads one of the fibres 4 to the suitably
positioned ferrule 23. It will be appreciated that the user, having
guide members 16 and the ferrules 23 selectively engageable with
the web at any desired position can store the fibre on the
connecting member and secure it thereto without exceeding the
minimum bend radius dictated by the fibre. At an appropriate stage
of the operation the electric conductors are led underneath the
plate 5 and joined. The external housing is then applied.
Other embodiments are specifically envisaged. A perforated cylinder
would provide a large area surface for receiving guides and
ferrules. Alternatively several flat perforated plates could be
assembled into an array polygonal in cross section. In these
embodiments the fixing of the cable strength members will probably
not be made on the perforated member.
* * * * *